The present invention relates to an apparatus for mass-supplying a semiconductor process gas, more specifically to an apparatus for mass-supplying a semiconductor process gas which supplies a semiconductor manufacturing process gas such as monogermane, monosilane, disilane, diborane, arsine, phosphine, hydrogen selenide, hydrogen chloride, hydrogen bromide, silicon tetrachloride, nitrogen trifluoride, methane tetrafluoride, ethane hexafluoride, dinitrogen monoxide, sulfur hexafluoride and ammonia in a large amount safely using a compact system.
The quantity of semiconductor process gases employed in the semiconductor industries is increasing with the increase in the number of wafers treated per plant, and a further increase is estimated in treatment of 300 mm (12 inch) wafers. Further, most of semiconductor process gases or fluid generally have combustibility, toxicity and corrosive properties. Those gases having particularly high combustibility and high toxicity such as monogermane, monosilane, disilane, diborane, arsine, phosphine and hydrogen selenide are special high-pressure gases which should satisfy requirements in terms of technique and equipment defined by the safety standard under the law, self-imposed control, etc. Under such circumstances, maintenance of safety is now the essential factor. With an impending necessity of mass supply of semiconductor process gases with the increase in the diameter of wafers, these gases need to satisfy safety requirements more strictly.
Higher quality is required in semiconductor process gases as devices are more and more refined, and particularly reduction of moisture, oxygen and oxygen compounds, as well as metal impurities and particles, which are decisive factors for device failure, is strictly demanded.
Usually, semiconductor process gases are charged in high-pressure vessels (cylinders) in gas charging plants, and the cylinders are loaded on autotrucks and transported to semiconductor manufacturing plants where they are stored temporalily in high-pressure gas storages for semiconductor process gases. When a semiconductor process gas is to be consumed, the high-pressure cylinder is housed in a cylinder cabinet so as to secure safety, and then the gas charged in the cylinder is supplied to a semiconductor processing apparatus.
In the case where a semiconductor process gas is supplied using an ordinary bomb or cylinder having a capacity of 47 liters or less, a gas cylinder valve attached to the cylinder is connected to a pressure reducing valve located in the cylinder cabinet, and the gas is subjected to pressure reduction before it is supplied to a semiconductor processing apparatus. Meanwhile, the cylinder cabinet is provided with a purge gas cylinder, a purge gas line and a detoxicating unit for the semiconductor process gas and has a structure such that the atmospheric air components migrating thereto during replacement of the gas cylinder or a purge gas can be replaced with the semiconductor process gas. The cylinder cabinet is also provided with an alarm capable of detecting gas leakage in the cylinder and a gas supply line for maintenance of safety. A main valve of the gas cylinder is originally equipped with an emergency shut-off function or an emergency shut-off valve is located in addition to the main valve so as to shut off supply of the gas in case of detection of any gas leakage. Usually, the gas in the cylinder cabinet is normally exhausted, and the cylinder cabinet has a mechanism for achieving detoxication of a leak gas with the aid of a scrubber and detoxicating unit connected to the cylinder cabinet.
When a semiconductor process gas is supplied in a large amount, the so-called bundled system having several tens of ordinary 47-liter cylinders bundled into one unit or the loader system having an assembly of 5 to 20 cylinders with an outside diameter of 300 mm or more (particularly 350 to 400 mm) and a length of 1.5 m to 12 m is employed. Thus, it is actually impossible to house xe2x89xa747-liter cylinders in the cylinder cabinet. Therefore, a large cylinder is located outdoors so as to cope with mass supply of a semiconductor process gas, and a gas supply panel containing a pressure reducing valve is disposed adjacent to the cylinder so that the gas is supplied through this panel.
FIG. 1 shows a schematic drawing explaining the bundled system gas supply apparatus. In this apparatus, ten 47-liter cylinders 10 are connected by a manifold 12 via cylinder valves 11 and are housed together in a frame 13. The manifold 12 is connected by a joint 20 via a valve 14 and a pipe 15 to a pipe 19, having a pressure reducing valve 17 and a closing valve 18, in a gas receiving equipment 16 installed in a plant where the gas is used. Two bundled system gas supply apparatuses are arranged in the plant and are used selectively. Accordingly, the upstream side and the downstream side of the pressure reducing valve 17 constitute a high-pressure gas region H and a low pressure gas region L respectively.
However, the conventional semiconductor process gases are frequently charged in cylinders at the pressure of not less than 1 Mpa. In the gas supply method resorting to such gas supply apparatus, there is a long distance between the cylinders 10 and the gas receiving equipment 16, so that the piping through which the high-pressure gas flows without pressure reduction is long, and that maintenance of safety becomes that much severe and difficult. Thus, the distance of the piping in the high-pressure gas region H connecting the manifold 12 with the pressure reducing valve 17 ranges over several tens of meters, and the high-pressure gas is as such allowed to flow through the piping laid over a long distance in a semiconductor plant.
Further, since the manifold 12 is connected at many joints with the gas cylinder valves 11 of the cylinders, the liability of leakage increases. In other words, factors dominating safety in terms of handling of semiconductor process gases are decided depending on the length of the high-pressure gas region H and the number of sections where leakage can occur (e.g., fitting) in supplying a semiconductor process gas.
Further, semiconductor process gases to be supplied are required to have high purity so as to maintain product quality. The quality of a semiconductor process gas depends on whether purging of atmospheric air components during cylinder replacement is achieved well or not. Meanwhile, the semiconductor process gas reacts, on metal surfaces to be brought into contact with the gas, with moisture adsorbed thereon or oxygen or undergoes autolysis to form corrosion products or by-products. Thus, the state of gas contact surfaces changes with elapse of time, and the amount of adsorbed water, the amount of intruded oxygen and particle count which cause pollution in the piping during cylinder replacement also change, so that the conditions of purging the atmospheric air components are caused to change inevitably. Since it takes much time for purging the atmospheric air components, and since it is impossible to estimate whether the atmospheric air components are fully removed or not even if much time is spent for the purging, it happens occasionally that the atmospheric air component moisture and oxygen, or particles cause pollution in the semiconductor processing apparatus; or that the semiconductor process gas reacts with the moisture and oxygen to form oxygen compounds, particles, in turn, corrosion products, and such by-products cause pollution in the semiconductor processing apparatus, to be causative of deterioration of electric performance of the resulting devices and reduction in the yield.
It is a first objective of the present invention to provide a gas supply apparatus which has a reduced installation space and can cope with use of a mass of gas.
It is a second objective of the present invention to enhance purging performance of the gas supply system and to prevent entry of impurities into the processing apparatus so as to supply a high-purity semiconductor process gas which is used in a large amount safely and without reduction in the purity thereof.
It is a third objective of the present invention to realize a gas supplying cylinder equipment which facilitates safety control and can maintain safety by reducing the section filled with a high-pressure gas (high-pressure gas region) where gas leakage is likely to occur to reduce the liability of leakage and by reducing the space for pipes in the gas supply line and joints therein.
In the apparatus for supplying a semiconductor process gas charged in a large-capacity gas cylinder to a plant where the gas is used after reduction of the pressure of the gas according to the present invention, the gas cylinder is composed essentially of a cylindrical portion and hemispherical portions formed at the ends of the cylindrical portion respectively. The gas cylinder also has a gas charge port at one hemispherical portion and a gas discharge port at the other hemispherical portion, so that the ports open in alignment with the axis of the cylindrical portion. A charge valve and a gas discharge unit having at least a gas cylinder valve and a pressure reducing valve are connected to the gas charge port and the gas discharge port respectively. The gas cylinder is housed together with the charge valve and the gas discharge unit in a container.
Since the high-pressure section is reduced by connecting the gas discharge unit having a gas cylinder valve and a pressure reducing valve to the gas discharge port which is a high-pressure gas section where gas leakage is likely to occur, and since the gas cylinder is housed together with the charge valve and the gas discharge unit in the container, high security can be maintained against gas leakage and the like even if a large-capacity gas cylinder is used. In addition, if two pressure reducing valves are arranged in series in the gas discharge unit, two-step pressure reduction can be implemented.
The mass supply apparatus is provided with at least one selected from an alarm for detecting gas leakage in the container; exhaust means for exhausting the gas in the container; and a purge gas cylinder charged with a purge gas for effecting purging in the gas discharge unit. A gas supply unit is connected to the gas discharge unit outside the container. The gas supply unit contains a supply valve connected on the downstream side to a piping of the plant where the gas is used, a purge gas inlet passage and an analysis gas outlet passage connected to the upstream side of the supply valve. The mass supply apparatus is provided with at least one selected from a detector for analyzing impurities contained in a gas to be purged out when the gas discharge unit is connected to the gas supply unit; and a detoxicating column for detoxicating the gas to be exhausted by the purging before the gas discharge unit is separated from the gas supply unit. In the mass supply apparatus, a plurality of containers can be selectively connected to one gas supply unit.
The footprint of the gas supply apparatus in a semiconductor plant where the gas is used can be minimized by connecting a plurality of containers selectively to a gas supply unit.